all: cleanup the APIs for initializing genesis (#25473)

* all: polish tests

* core: apply feedback from Guillaume

* core: fix comment

cmd/devp2p/internal/ethtest/chain.go

@@ -139,7 +139,7 @@ func loadChain(chainfile string, genesis string) (*Chain, error) {
 	if err != nil {
 		return nil, err
 	}
-	gblock := gen.ToBlock(nil)
+	gblock := gen.ToBlock()
 
 	blocks, err := blocksFromFile(chainfile, gblock)
 	if err != nil {

cmd/evm/runner.go

@@ -138,7 +138,7 @@ func runCmd(ctx *cli.Context) error {
 		gen := readGenesis(ctx.String(GenesisFlag.Name))
 		genesisConfig = gen
 		db := rawdb.NewMemoryDatabase()
-		genesis := gen.ToBlock(db)
+		genesis := gen.MustCommit(db)
 		statedb, _ = state.New(genesis.Root(), state.NewDatabase(db), nil)
 		chainConfig = gen.Config
 	} else {

cmd/faucet/faucet.go

@@ -248,7 +248,7 @@ func newFaucet(genesis *core.Genesis, port int, enodes []*enode.Node, network ui
 	cfg.SyncMode = downloader.LightSync
 	cfg.NetworkId = network
 	cfg.Genesis = genesis
-	utils.SetDNSDiscoveryDefaults(&cfg, genesis.ToBlock(nil).Hash())
+	utils.SetDNSDiscoveryDefaults(&cfg, genesis.ToBlock().Hash())
 
 	lesBackend, err := les.New(stack, &cfg)
 	if err != nil {